Packaged microelectronic assemblies, such as memory chips, imagers, and microprocessor chips, typically include a microelectronic die mounted to a substrate and encased in a plastic protective covering or encapsulant. The die includes functional features, such as memory cells, processor circuits, and interconnecting circuitry. The die also typically includes bond pads electrically coupled to the functional features. The bond pads are electrically connected to pins or other types of terminals that extend outside the protective covering for connecting the die to busses, circuits, and/or other microelectronic assemblies.
One approach for carrying a microelectronic die in a package is to support it on an interposer board or other type of circuit board. The interposer board can include a first set of bond pads to which the microelectronic die is electrically connected with wire bonds or solder balls. Conductive traces route electrical signals between the first set of bond pads and a second set of bond pads that are accessible from outside the package encapsulant for connections to other devices.
Customer demands have resulted in increasing pressure on manufacturers to make the encapsulated microelectronic die packages smaller. In response, some manufacturers have recessed the microelectronic die in the circuit board to reduce the thickness of the resulting package. One approach to recessing the microelectronic die is to (a) form a cavity extending entirely through the circuit board, (b) place a layer of a removable adhesive across one opening of the cavity, and then (c) temporarily support the die in the cavity with the adhesive while the die is electrically connected to the circuit board. The die is then encapsulated in the cavity, which both secures the die to the circuit board and protects the electrical connections between the die and the circuit board. The adhesive layer is then removed.
One potential drawback with the foregoing approach is that it requires the use of a removable adhesive layer to temporarily secure the die to the circuit board during manufacture. The operation of first attaching the removable adhesive layer and then detaching the removable adhesive layer can add to the overall flow time required to produce the microelectronic device package. This can in turn reduce the throughput of a package production line, and/or increase the cost of producing such packages.